1. Field of the invention
This invention relates generally to the field of fishery studies where egg and larvae density, survival, and development and/or timing and duration of fish reproduction are necessary, and more particularly to a method and apparatus for unattended, continuous collection and preservation of fish egg and larvae samples.
2. Prior art of interest
In both environmental impact studies and marine biological research programs, it is very often necessary to determine the abundance and distribution of fish life at various depths along the water column. Past practices relating to collecting small aquatic animals or larvae in large quantities fail to provide reliable data on fish spawning that is missed with conventional daily or weekly sampling. One such sampler is disclosed in U.S. Pat. No. 3,967,585 to Monaco which discloses a larvae collection system which comprises a container for water being open at one end and closed at the other, a fluid inlet means to the container, a fluid conduit means positioned within and extending about the vertical length of the container and passing through the bottom of the container, a fluid outlet means positioned in the upper portion of the conduit, and a screening means positioned between the side walls of the container and the fluid outlet means so that the animals are retained in the container in sufficient water, while excess water passes through the screen and out the outlet means.
U.S. Pat. No. 3,040,980 to Mann et al discloses a method and apparatus for counting mobile aquatic creatures comprising a first enclosure to confine and guide aquatic creatures to be counted to a short conduit or tube having windows on each side for the passage of a light beam passing from window to window. A light source and a photo electric responsive device are used to count the creatures.
U.S. Pat. No. 4,718,192 to Louk discloses a hydromechanical bait trap including a field of prearranged conduit sections or runs and the conduit assembly includes inlet and outlet ends. The conduit assembly is designed to be supported adjacent the bottom of a shallow pond and includes a partially submerged mesh sump into whose lower portion the inlet end of the conduit assembly opens and the outlet end of the conduit assembly discharges downwardly into the sump, the sump being adapted to receive ground or finely cut-up bait. A pump is serially connected in the inlet and the conduit sections comprising the field include a plurality of lateral branches opening into the runs and mounted therefrom for annular displacement thereabouts between lower generally horizontal positions and upstanding upright positions projecting above the pond water level. The free ends of the lateral branches include marine trap structures and structure is provided for simultaneously raising and lowering the lateral branches.
Other prior art devices for sorting or grading marine life are shown by U.S. Pat. No. 3,096,600 to Gwyther, U.S. Pat. No. 4,028,821 to Hanks, U.S. Pat. No. 4,198,925 to Lindberg, U.S. Pat. No. 4,351,127 to Mitchell, and U.S. Pat. No. 4,986,021 to Thomas. None of the prior art devices are specifically designed for continuous egg and larvae collection. Automatic plankton samplers have limited ability to collect fish eggs and larvae because they are not designed to filter larger volumes of water continuously and have smaller mesh filter screens.
The fish egg and larvae collection system of the present invention solves the problems presented by the prior art by the novel use of methods to gently handle eggs and larvae, increase frequency of sample, automate preservation and simplify operation so it could be run by non-technical field workers.